Prestige crit bonus / potency conversion problem

I made some test with my coercer with the consersions:

potency -> crit bonus : 12/1 ratio with only one conversion
potency -> crit bonus : 24/1 ratio with only both conversion

crit bonus -> potency : 3/1 ratio with only one conversion
crit bonus -> potency : 7/1 ratio with only both conversion

I check the actual values and I found that there is a bug on double conversion:

the 24/1 ratio on potency -> crit bonus is correctly applied
but the 7/1 is not, actually the crit bonus -> potency stats at 3/1

by the way why the it is 7/1 instead of 6/1 ? in the end that will not make much a difference compare to what we get with the deity points